First Time-Resolved Characterization of Fusion Neutron Spectra via a Liquid Scintillation Detection System in the HL-3 Tokamak

We present, for the first time, our recent advancements in time-resolved fusion neutron spectra measurements and analyses within the HL-3 tokamak. The measurements are executed using a liquid scintillation detector, which has the capacity to discriminate neutrons and -rays. Notably, the liquid scintillation detector directly acquires the pulse height spectra of recoil protons in the liquid scintillator, rather than the neutron spectra themselves. To convert the pulse height spectra of recoil protons into neutron spectra, Geant4 simulations are performed to compute the detector response matrix. Subsequently, the GRAVEL method is employed in the neutron spectrum unfolding process. As a result, the time-resolved neutron energy spectra can be obtained through time-resolved pulse amplitude spectra measurements. In this study, the optimal time-resolution for the neutron spectra is 100 ms. This indicates that the HL-3 tokamak is equipped with the ability to conduct research on the temporal evolution of neutron spectra and fast ion velocity distributions.